This invention relates to an air bag assembly, and more particularly to an air bag assembly including an inflatable air bag cushion and one or more selectively actuated vents across the surface of the air bag cushion. The vents are selectively actuated in conjunction with control of the inflated profile of the air bag cushion such that venting is properly matched to the inflated profile characteristics of the air bag cushion. The venting characteristics of the air bag cushion and the profile of the air bag cushion may be controlled by the selective adjustment of tethering elements based upon the measured size and/or position of the vehicle occupant to be protected.
It is well known to provide an air bag assembly including an inflatable air bag cushion for protecting the occupant of a transportation vehicle. In an automotive vehicle such air bag assemblies are typically located within the hub of the steering wheel and in a recess in the vehicle instrument panel for protection of the vehicle occupants seated in opposing relation to such assemblies. Additional air bag assemblies may be located within the seats and/or door panels for protection of the occupants during a side-impact event. It is also known to utilize inflatable curtain-like structures for deployment from the structural pillars or roof line of the motor vehicle so as to promote restraint and protection of the vehicle occupant during a roll-over event.
Air bag assemblies typically include an inflatable cushion in fluid communication with a gas emitting inflator. Upon sensing certain predetermined vehicle conditions, such as a certain level of vehicle deceleration, the inflator discharges a fixed amount of inflator gas thereby forcing the air bag into a deployed position. The inflator gas occupies the available volume within the air bag cushion thereby forcing the air bag cushion to expand outwardly to the extent permitted by its construction. The pressure within the air bag cushion upon deployment is proportional to the quantity of inflator gas expelled into the air bag and inversely proportional to the volume occupied by the inflator gas within the air bag. As the occupant comes into contact with the expanded air bag, the inflator gas is forced out of the air bag thereby dissipating the kinetic energy of the occupant achieving a so called xe2x80x9cride downxe2x80x9d effect. In order to facilitate the discharge of inflator gas from the air bag it is common to incorporate vents in the form of normally open fixed diameter apertures across the walls of the air bag. As pressure increases at the interior of the air bag the rate of venting is correspondingly increased. Thus, while the rate of gas venting is relatively low during the initial inflation, gas venting is increased as inflation is completed and pressure inducing impact takes place between the occupant and the air bag.
It has been recognized that in some instances it may be desirable to adjust the inflation characteristics of the air bag to reflect the nature of the impact event and/or the size and/or the position of the occupant to be protected. In order to provide a degree of control over the gas pressure within the air bag cushion it is known to use an inflator that has varied levels or stages of inflator gas output in response to the sensing of different vehicle or occupant conditions. Thus, it is generally known in the prior art to utilize so-called xe2x80x9cdual-stagexe2x80x9d inflators that discharge predetermined amounts of gas at different discrete levels. However, these dual-stage inflators are more complex than typical inflators and have the limitation of typically providing only discrete levels of gas output.
In order to provide additional control over the inflation characteristics of the air bag cushion it has been suggested to utilize tethering elements in the form of straps or webs extending between surfaces of the air bag which may be released from a first restrained operative length to a second extended operative length upon the occurrence of vehicle conditions warranting an increased air bag profile. It has also been suggested to utilize air bag cushions which incorporate sewn or woven in seams within the air bag to control the expanded geometry of the inflated air bag wherein the seams separate upon the introduction of pressures exceeding a certain level thereby freeing the air bag cushion from the restraint imposed by the seams at lower pressures.
While the various known systems for controlling the shape of the air bag cushion and the volume of inflation gas entering the air bag cushion are believed to provide a number of benefits to a user, such systems have heretofore not provided adjustment to the venting character of the air bag cushion.
The present invention provides advantages and alternatives over the prior art by providing an air bag assembly including one or more selectively activatable vents which may be either opened or closed in conjunction with adjustment of the cushion profile characteristics such that venting is selectively controlled in a predefined manner.
According to one aspect of the present invention, an air bag assembly is provided having an inflatable cushion selectively deployable to a controlled geometry with a controlled venting character desired in view of crash severity and/or the position of the occupant to be protected and/or the size of the occupant to be protected such that an air bag of desired volume and venting capacity matched to the impact and occupant conditions is available to protect a range of occupants during impact events of various severity.
The air bag assembly provides a simple, cost effective and highly reproducible mechanism for controlling the venting character of the air bag cushion in conjunction with control of the profile and performance of deployed air bag cushions even when using a traditional single stage inflator.